The connector is provided with a locking mechanism capable of engaging and disengaging with each other a receptacle and a plug. The receptacle is provided with a first housing and a first contact. The plug is provided with a second housing and a second contact. The first housing has at a recess portion a lock arm provided at its end with a hook portion. The second housing has at a header portion an engaging protrusion. When the header portion is inserted into the recess portion, the engaging protrusion rides over the hook portion, and the complete fitting of the receptacle and the plug can be felt. When the header portion is pulled out from the recess portion, the hook portion is displaced, and the plug can be readily pulled out from the receptacle.